Numbers Property, Geometry, Algebra, Foundations of GMAT MATH
, and Foundations of GMAT VERBAL, Manhattan Gmat Sentence Correction
, if you just started studying, get familiar with the manhattan gmat books
, in my opinion, you should fork out the 200 bucks, buy them new, and buy the whole set, you'll get the OG Guide #13, and mainly all the tools you'll need to accomplish this task. Books are pretty straightforward, and will teach you the fundamentals for the GMAT. If you buy everything new, you'll get a bunch of question banks + the 6 online CAT exams on the MGMAT.com website, and this will help you strengthen what you've learned on the text book, they cover it all.
Kudos if this helps!